Applying images to paper products by utilizing pigment based ink compositions is well known in the art. One of the difficulties historically experienced with sanitary disposable paper products (including facial tissue, bath tissue, table napkins, wipes, and cotton pads) printed with pigment based ink compositions is the tendency for the ink to rub-off of the surface of the paper upon exposure of the paper to liquids. The problem is even more pronounced for those sanitary disposable paper products printed with inks exhibiting relatively high color densities.
The tendency for the ink to rub-off increases as the printed sanitary disposable paper product is exposed to liquids such as tap water. Furthermore, exposing the sanitary disposable paper product printed with ink to common household cleaning products containing solventized alkaline liquids, or acid-containing cleaning liquids tends to increase ink rub-off as compared to exposure of the paper towelling to tap water alone.
U.S. Pat. No. 3,642,502 issued to Schneider on Feb. 15, 1972 teaches a bleed resistant ink composition comprising a coloring material, polyamide epichlorohydrin, talc, and a solvent for printing on paper products.
This teaching neither addresses sanitary disposable paper products having high color density images, nor does it address images produced from water-based pigment containing ink compositions which exhibit resistance to ink rub-off.
The benefit of the present invention is the ability to provide a sanitary disposable paper product exhibiting high color density images while exhibiting resistance to ink rub-off. A further benefit of the present invention is the ability to provide a sanitary disposable paper product which exhibits high color density images while exhibiting resistance to ink rub-off upon exposure to a wide variety of liquids across a broad pH range including but not limited to water and common household cleaners such as alkaline-based, solvent-based, surfactant-based, and acid-based cleaners. Yet a further benefit of the present invention is the ability to provide a sanitary disposable paper product which exhibits resistance to ink rub-off without requiring the addition of a separate prophylactic coating over the ink.